Hierarchical porous organic polymers via the in situ construction of the BINOL entity: versatile and efficacious adsorbents for multiple industrial toxic contaminants in water

Abstract

An efficient synthetic route for the generation of BINOL-based porous organic polymers (POPs) with hierarchical porosity has been developed. As opposed to BINOL-based POPs reported in the literature, which are mostly synthesized from commercial BINOL-based monomers, herein, we generated the BINOL moiety in situ during the polymerization of 2-naphthol-based monomers to achieve our BINOL-based POPs. These BINOL-based POPs showed a high BET surface area of up to 595 m² g⁻¹, good thermal stability up to 328 °C (for BINOL-POP-2), and a hollow tube-like morphology (for BINOL-POP-1). They exhibited the selective adsorption of various cationic and neutral dyes compared with anionic dyes in water with an excellent removal efficiency (>99%) and ultrafast kinetics (k = 5.21 min⁻¹ for capturing methylene blue). The maximum adsorption capacity (Q_max) for these BINOL-based POPs reached 1941 mg g⁻¹ for propidium iodide, 1639 mg g⁻¹ for neutral red and 1390 mg g⁻¹ for ethidium bromide, which are so far the highest values reported for these dyes. In addition, these POPs could also effectively capture textile dyes, nitroaromatic compounds and toxic bisphenol-A, thus demonstrating these BINOL-based POPs to be versatile adsorbents. Moreover, these POPs are fully recyclable for at least five cycles without losing their adsorption efficiency significantly.